2 .   The steam supply line from the boiler 3  .   The water overflow line 4.   The water supply line from the reservoir The controls for the injector (fig. 1-13) include the following: A.  Steam  supply  valve B. Water supply valve C. Discharge valve to the boiler D. Check valve in the discharge line As you might expect. some degree of skill is needed to start the injector. After the injector begins to operate. however, it continues automatically until shutdown by the  operator. When  starting  the  injector.  first  open  the  water supply  valve  (fig.  1-13B)  about  one  full  turn. Nest quickly turn the steam supply valve (fig. 1-13A) all the way open. At this point, steam rushes into the combining tube of the injector As the steam speeds past the water supply opening. it creates a suction that draws water through the opening into the combining tube. Water and steam are now mixed together inside the injector and the pressure  opens  a  valve  that  leads  to  the  boiler. Meanwhile. there is an excess of water in the injector; this excess is discharged through the overflow valve. As the nest step of the procedure, slowly turn the water supply valve (fig. 1-13B) toward the closed position until the overflow stops.   The overflow valve has now closed and all of the water being picked up from the supply line is going into the boiler. Remember, this feedwater system is used on boilers only as a standby method for feeding water. The water supply should not be hotter than 120°F for the  injector  to  operate.  When  several  unsuccessful attempts are made to operate the injector. it will become very hot and cannot be made to prime. When you should encounter this problem. pour cold water over the injector until it is cool enough to draw water from the supply when the steam valve is opened. HANDHOLES AND MANHOLES Handholds   and   manholes   provide   maintenance personnel access into a boiler to inspect and clean it internally  as  needed.  These  handholds  and  manholes  will be  covered  in  depth  when  boiler  maintenance  is discussed later in this volume. BOILER ACCESSORIES Figure  1-14  provides  a  graphic  presentation  of important boiler accessories. Refer to it as you study the table  1-2  which  gives  a  brief  description  of  each accessory, its location, and function. Learning  Objective:  Identify the automatic controls commonly  used  on  boilers  and  describe  the  function  of each. Automatic controls are a big asset since they reduce manual  control  of  the  furnace.  boilers.  and  auxiliary equipment.  For  this  reason.  Utilitiesman  personnel should be able to recognize and understand the basic operations of different types of boiler operating controls. The types of controls the Utilitiesman should become familiar with are as follows: float. pressure, combustion. flame failure. and operation controls. FLOAT CONTROL The float in a boiler control works on the same basic principle as the float in a flush-tank type of water closet. Float, or level, control depends on the level of fluid in a tank or boiler to indicate the balance between the flow out of  and  the  flow  into  the  equipment  and  to  operate  a controller to restore the balance. A float is often used to measure the change in fluid level and to operate the controlled valve to restore the balance. It may be arranged to increase the flow when the fluid level drops. Figure 1-15 shows one of the methods used to accomplish this. Here, the float is connected to the control  valve. Q9.   Blowdown valves are installed at what location in a  boiler? Q10.  How often should the fusible plugs in a boiler be renewed? Q11. The  two  connections  to  the  boiler  of  a  water column are at what locations? Q12.  What are the three types of water level controls most often encountered by Seabees? Q13. The electrode probe type of feedwater control has what  total  number  of  electrode  sensors? Q14. What   boiler   fitting   is   considered   the   most important? Q15.  What is the function of the guard valve on a boiler? AUTOMATIC   CONTROLS 1-14